Biouminescence is a process wherein living organisms emit light in the course of a biochemical reaction wherein chemical energy transforms into light energy. Several types of bioluminescent systems have been described.
For example, the systems of a number of marine coelenterates comprising aequorin proteins have been described (Prasher, et al., Biochem. 1987, 26:1326-1332; Tsuji et al., Photochem Photobiol, 1995 62(4):657-661). The aequorin family also comprises obelin, halistaurin (mitrocomin), phiallidin (clytin), etc. These are photoproteins comprising luciferin which is covalently bound thereto. In the presence of Ca2+ ions, luciferin undergoes chemical changes resulting in the formation of a product in an excited state.
The components of the bioluminescent systems (luciferases, photoproteins, luciferins, etc.) are commonly used reagents in a plurality of assays including diagnostic systems, quality control systems, etc. For example, aequorin and its homologs are commonly used in studying the release and fixation of Ca2+ in biological systems; for example, during a muscle contraction. For example, the use of the bioluminescent systems has been described in detail in Cormier, M. L. et al., Photochem. & Photobiol. 49/4, 509-512 (1989), Smith, D. F. et al. in “Bioluminescence and Chemiluminescence: Current Status (P. Stanley & L. Krick, eds.), John Wiley and Sons, Chichester, U.K. 1991, 529-532.
The discovery of the new components of bioluminescent systems makes it possible to broaden the spectrum of available assays and applications.
Bioluminescence of higher fungi is commonly known. The fruiting bodies of many fungi are capable of producing constant light which can be clearly seen by an unaided eye. Luminescence of the extracts of bioluminescent fungi was first demonstrated in 1959 (R. L. Airth and W. D. McElroy, Light emission from extracts of luminous fungi, J. Bacteriol., 1959, 77, 249). Light was produced in response to adding NADPH to the mixture of “cold” and “hot” extracts made of fungal mycelia of Collybia velutipes and Armillaria mellea. 
As used herein, the term “cold extract” refers to an extract comprising the enzymes of the fungal bioluminescent system and free from low-molecular-weight components of the system. In order to obtain the cold extract, the following protocol may be used: wash the biomass of fungal mycelium to get rid of culture medium, then put the biomass into sufficient amount of distilled water (1:100-1:200 by mass) for 15-16 hours at the temperature of 26° C. After steeping, collect the biomass and freeze at −20° C. Then, thaw the biomass and rinse with distilled water a few times. Pour 0.01 M phosphate buffer (pH 7.5) over the mycelium with a mass to volume ratio of 1:10. Then, using a homogenizer, grind and ultrasound (for example, using Ultrasonic disintegrator UD-20 (Techpan, Poland) or a similar device) on ice 5 times for 1 minute in 1 minute intervals. Centrifugate the obtained homogenate at 30000 g for 20 minutes at 4° C.
As used herein, the term “hot extract” refers to an extract comprising the low-molecular-weight components of the system and free from the enzymes of the fungal bioluminescent system. In order to obtain a hot extract, the following protocol may be used: wash the biomass of fungal mycelium to get rid of culture medium, then put the biomass into sufficient amount of distilled water (1:100-1:200 by mass) for 5-6 hours at the temperature of 26° C. After steeping, collect the biomass and heat to boiling. Then, quickly cool on ice and centrifugate at 30000 g for 20 minutes.
Studies on bioluminescence of higher fungi have led to the conclusion that bioluminescence is based on a general two-stage process as follows: the first stage is formation of luciferin from a precursor catalyzed by a NAD(P)-H-dependent enzyme; the second stage is oxidation of luciferin under luciferase catalysis accompanied by t the emission of visible light (R. L. Airth, Characteristics of cell-free fungal bioluminescence, in Light and Life, ed. W. D. McElroy, B. Glass, Johns-Hopkins Press, Baltimore, 1961, pp. 262). However, until present, the chemical nature of the components of the bioluminescent system of higher fungi has not been established.
In 1966, Kuwabara and Wassink described luciferin emission from Omphalia flavida, but they did not provide any data on its chemical structure (S. Kuwabara and E. C. Wassink, in Bioluminescence in Progress, ed. F. H. Johnson and E. Y. Haneda, Princeton University Press, Princeton, 1966, p. 233). In 1970, Endo et al. isolated a fluorescent component from Pleurotus japonicus with fluorescence emission maximum at 530 nm (which is close to the emission maximum of fungal bioluminescence). This component was called illudin S. However, this substance did not show bioluminescent activity (M. Endo, M. Kajiwara and K. Nakanishi, Chem. Commun., 1970, 309). Later, in 1987-1988, Isobe et al. isolated riboflavin and lampteroflavin from the same source with the fluorescence emission maximum at 524 nm. However, these substances also did not show bioluminescent activity (M. Isobe, D. Uyakul and T. Goto, J. Biolumin. Chemilumin., 1987, 1, 181; M. Isobe, D. Uyakul and T. Goto, Tetrahedron Lett., 1988, 44, 1169). The candidates to the role of luciferin have also been isolated from Mycena chlorophos (S. Hayashi ey al. 2012. Biophysics Vol. 8, pp. 111-114) and Panellus stipticus (O. Shimomura et al. J Biolumin. Chemilumin. 1993, 8, 201-205; O. Shimomura et al Tetrahedron 1988, 44, 1597-1602, O. Shimomura Bioluminescence: Chemical Principles and Methods. CHAPTER 9 LUMINOUS FUNGI 2006, World Scientific, Singapore). However, no evidence has been provided in regard to their participation in bioluminescence. In 2009, Oliveira and Stevani described the isolated components of the bioluminescent systems of several fungi species: Gerronema viridilucens, Mycena lucentipes and Mycena luxaeterna (A. G. Oliveira and C. V. Stevani, Photochem. Photobiol. Sci., 2009, 8, 1416). They pointed out that the study on their structure was complicated due to a low concentration and low stability of these substances. The recent works of these researchers concerning a wide range of fungi have shown cross-reactions of “hot” and “cold” extracts of different species, thus proving a universal mechanism and similarity of the bioluminescent systems of all kinds of higher fungi (Oliveira et al. Photochemical & Photobiological Sciences 2012, 11 (2): 848-52, Stevani et al. Photochemistry and Photobiology, 2013, 89: 1318-1326).